Video communications has evolved over the years from a simple video telephone concept to a sophisticated network for allowing multiple users to participate in a video teleconference. For full featured video teleconferencing, users require both an audio communications path and a real time visual communication path synchronized to the audio path. Furthermore, it is desirable to support full color video and telephone quality audio. Video teleconferencing capabilities are limited mainly by the bandwidth of the transmission medium connecting the teleconferencing terminals.
Many computer workstations used in the office or laboratory environment today are connected with other workstations, file servers, or other resources over high-speed local area networks. Local area networks, in turn, are often connected together through high-speed gateways which connect workstations which may be distributed over a wide geographic area. Network wide protocols allow workstations to exchange packets of data at high rates of speed and reliability. Fixed bandwidth digital and analog video channels have been combined with computer networks to implement some video teleconferencing features. These include high bandwidth CATV/FDM type analog channels and fixed allocation TDM data channels for the video data.